by Paul Davidson, USA TODAY

by Paul Davidson, USA TODAY

Senate Republicans are likely to press Federal Reserve Chair Janet Yellen Tuesday for a more specific timetable for raising short-term interest rates as the labor market and inflation continue to pick up steam.

Economists, however, expect Yellen to largely deflect such questions, reiterating that the path of interest rates depends on how quickly the economy continues to progress during an uncertain period.

Yellen is scheduled to deliver her semi-annual report on monetary policy to the Senate Banking Committee as the Fed grapples with myriad challenges.

On one hand, employment gains have improved noticeably this year, even while broader economic growth has been disappointing. Meanwhile, a measure of inflation the Fed watches closely has risen close to its annual 2% target, in part because of sharply rising food and energy prices.

The improving labor market has prompted Fed policymakers to gradually taper monthly bond purchases aimed at holding down long-term interest rates and spurring economic activity. The bond buying is expected to end in October.

Fed officials also have indicated that, sometime in 2015, they will likely begin to raise short-term interest rates, which have hovered near zero since the 2008 financial crisis.

The interest rate forecasts of Fed policymakers suggest the Fed's first rate hike could come in mid-2015, but some economists have said that accelerating inflation will force the Fed to raise rates early next year. Some Fed officials also have argued that the central bank should raise rates if potentially dangerous asset bubbles begin to form in certain markets.

Yellen, however, said in a speech last week that regulation should be its first line of defense against asset bubbles and that monetary policy should be used only as a last resort.

She also has downplayed the inflation data as "noisy." And she has said that despite the rapidly falling unemployment rate, the labor market is far from healthy, with long-term unemployment still near historical highs, and many Americans working part-time even though they want full-time jobs.

Citing the economy's conflicting signals, Yellen has repeatedly refused to specify when the Fed is likely to start raising short-term rates.

"The path of the economy is uncertain," Yellen said in an April speech, "and effective policy must respond to significant unexpected twists and turns the economy may take."

Jim O'Sullivan, chief US economist of High Frequency Economics, expects her to take a similar tack on Wednesday.

"Fed officials are emphasizing uncertainty more than usual," he wrote in a research note.